Biological Response and Antimicrobial Behaviour of Sputtered TiO2/Cu Coatings Deposited on Ti6Al4V Alloy

Nanostructured TiO2/Cu coatings were deposited on Ti6Al4V alloy by a two-step glow-discharge sputtering process and evaluated for their structural, electrochemical, and biological properties. Dual-acid etching produced microroughened substrates before TiO2 layer deposition, followed by surface Cu sputtering with varied deposition times. Characterisation by AFM, OM, SEM/EDS, and XRD confirmed the formation of TiO2 with Cu/Cu2O-containing hybrid coatings with good adhesion to the substrate. Increasing Cu deposition enhanced surface hydrophobicity and copper ion release. EIS measurements proved that the coatings retained stable protective behaviour in simulated body fluid (SBF). Antibacterial tests against Escherichia coli showed up to 98% improved efficacy compared to bare Ti6Al4V, confirming the strong antimicrobial role of copper. However, MG63 osteoblast-like cells exhibited reduced viability even after pre-immersion in PBS, suggesting that cytotoxicity was associated not only with excess Cu ion release but also with direct interaction between cells and surface Cu nanostructures. Overall, the results indicate that TiO2/Cu coatings provide excellent antimicrobial activity, good protection and strong adhesion, but their limited biocompatibility highlights the need for fine-tuned copper incorporation in future biomedical implant applications.